Western Blotting

Western blot analysis of extracts from RL-7 and 293T cell lines using EAF2 (E1R8C) Rabbit mAb.

Background

The super elongation complex (SEC) plays a critical role in regulating RNA polymerase II (RNAPII) transcription elongation (1). The SEC is composed of AFF4, AFF1/AF4, MLLT3/AF9, and MLLT1/ENL proteins. The pathogenesis of mixed lineage leukemia is often associated with translocations of the SEC subunits joined to the histone H3 Lys4 methyltransferase mixed lineage leukemia (MLL) gene (1-4). The SEC has been found to contain RNAPII elongation factors eleven-nineteen lysine-rich leukemia (ELL), ELL2, and ELL3, along with the associated factors EAF1 and EAF2, which can increase the catalytic rate of RNAPII transcription in vitro, (1,2,5-7). The SEC positive transcription elongation factor b (P-TEFb) phosphorylates the C-terminal domain within the largest subunit of RNAP II at Ser2 of the heptapeptide repeat. The SEC negative transcription elongation factors, DRB-induced stimulating factor (DSIF) and negative elongation factor (NELF), signal the transition from transcription initiation and pausing to productive transcription elongation (2,8-10). The chromosomal translocation of MLL with the members of the SEC leads to SEC recruitment to MLL regulated genes, such as the highly developmentally regulated Hox genes, implicating the misregulation and overexpression of these genes as underlying contributors to leukemogenesis (1,2,9,11).

ELL associated factor 2 (EAF2) was identified as an interacting partner of eleven-nineteen lysine-rich leukemia (ELL) (12). EAF2 (U19) has also been identified as a protein that is down-regulated in prostate cancers and exhibits growth inhibitory and tumor suppressive activity (13,14).